Sputtering Target for Magnetic Recording Medium, and Process for Producing Same

ABSTRACT

A sputtering target for a magnetic recording medium, wherein an average grain area of a B-rich phase is 90 μm 2  or less. A process for producing a sputtering target for a magnetic recording medium, wherein an alloy cast ingot is subject to heat treatment, thereafter subject to primary rolling which includes at least one pass of cold rolling, thereafter subject to secondary rolling, and machined to prepare a target. The obtained sputtering target for a magnetic recording medium has few cracks in the B-rich phase and has a high leakage flux density, and by using this target, it is possible to stabilize the discharge during sputtering, suppress arcing which occurs from cracks in the B-rich phase, and suppress the generation of particles.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 14/383,219 which is a 371 National Stage of InternationalApplication No. PCT/JP2013/055672, filed Mar. 1, 2013, which claims thebenefit under 35 USC 119 of Japanese Application No. 2012-053785, filedMar. 9, 2012

BACKGROUND

The present invention relates to a sputtering target for a magneticrecording medium for use in the deposition of a magnetic thin film of amagnetic recording medium, particularly for use in the deposition of amagnetic recording layer of a hard disk adopting the vertical magneticrecording system, and to a process for producing such a sputteringtarget.

In the field of magnetic recording as represented with hard disk drives,materials based on Co, Fe or Ni, which are ferromagnetic metals, areused as materials of a magnetic thin film in a magnetic recordingmedium. As the recording layer of hard disks adopting the verticalmagnetic recording system that has been put into practical use in recentyears, used is a composite material configured from a Co—Cr-based,Co—Cr—Pt-based or Co—Pt-based ferromagnetic alloy having Co as its maincomponent and nonmagnetic inorganic particles.

A magnetic thin film of a magnetic recording medium such as a hard diskis often produced by sputtering a ferromagnetic sputtering target madefrom foregoing materials via sputtering in light of its highproductivity. A hard disk drive that is used as an external recordingdevice is being demanded of a higher recording density year by year, andthere are strong demands for reducing the particles that are generatedduring sputtering pursuant to the increase in the recording density.

With a sputtering target for a magnetic recording medium made from aCo—Pt—B-based alloy or a Co—Cr—Pt—B-based alloy, since a discharge willnot occur during sputtering if the leakage flux density of thesputtering target is low, the voltage during sputtering needs to beincreased when the leakage flux density is low. Meanwhile, if thevoltage during sputtering is increased, there is a problem in thatarcing is generated or the voltage becomes unstable, and the generationof particles during sputtering increases. Thus, under normalcircumstances, cold rolling is perfoiined to artificially introducestrain and thereby increase the leakage flux density.

However, when the Co—Pt—B-based alloy or the like is subject to coldrolling, there is a problem in that the brittle B-rich phase in thealloy is subject to brittle fracture, and cracks are generated. Inaddition, the cracked B-rich phase becomes the source of arcing duringthe sputtering process, causes the generation of particles, anddeteriorates the production yield. In particular, when the area of theB-rich phase is large, since the stress concentration will increase bythat much, the strength will deteriorate, and the generation of crackswill increase even more.

Thus, considered may be preventing the cracks in the B-rich phase.Nevertheless, conventional technologies have no recognition of thisproblem, and do not propose any means for solving this problem. Forexample, Japanese Patent Application Publication No. 2001-026860discloses a Co—Pt—B-based target containing 1<B<10 (at %) and a methodfor producing such a target. With this production method, hot rolling isperformed at a temperature of 800 to 1100° C., and heat treatment isperformed at 800 to 1100° C. for 1 hour or longer before the hot rollingprocess. Moreover, Japanese Patent Application Publication No.2001-026860 describes that, while hot rolling is difficult when B iscontained, the generation of cracks of the ingot during hot rolling canbe inhibited by controlling the temperature. Nevertheless, JapanesePatent Application Publication No. 2001-026860 does not in any waydescribe the problem of cracks in the B-rich phase, or the relationbetween the size and cracks of the B-rich phase.

Japanese Patent Application Publication No. 2001-181832 disclosessputtering targets based on CoCrPt, CoCrPtTa, and CoCrPtTaZr containingB as an essential component. Japanese Patent Application Publication No.2001-181832 describes that, with this technology, the rolling propertiescan be improved by reducing the Cr—B-based intermetallic compound phase.As the production method and production process, Japanese PatentApplication Publication No. 2001-181832 describes performing vacuumdrawing at 1450° C., casting at a temperature of 1360° C., heating andholding at 1100° C. for 6 hours, and subsequently performing furnacecooling. Specifically, first time: heating at 1100° C. for 60 minutes,and thereafter rolling at 2 mm/pass, second time onward: heating at1100° C. for 30 minutes, and thereafter rolling up to 5 to 7 mm for eachpass. Nevertheless, Japanese Patent Application Publication No.2001-181832 does not in any way describe the problem of cracks in theB-rich phase, or the relation between the size and cracks of the B-richphase.

Japanese Patent Application Publication No. 2001-98360 discloses aCo—Cr—Pt—C-based target, wherein carbides having an average crystalgrain size of 50 μm or less exist in the matrix, and the carbidesexisting in the structure are dispersed when viewing the cross sectionof the target. The object of this technology is to prevent thegeneration of coarse crystals and thereby suppress variations in thecharacteristics of the magnetic film A Co—Cr—Pt—C-based material withlarge amounts of carbides containing C in an amount of 1 at % or morecan be subject to hot rolling, enables the refinement of the crystalgrain size and the dispersion of carbides, and suppresses variations inthe film characteristics such as the coercive force. Nevertheless,Japanese Patent Application Publication No. 2001-98360 does not describethe problem of cracks in the B-rich phase and the solution thereof.

Japanese Patent Application Publication Nos. 2006-4611 and 2007-02337respectively disclose Co—Cr—Pt—B—X1-X2-X3 and Co—Cr—Pt—B—Au—X1-X2. WhileJapanese Patent Application Publication Nos. 2006-4611 and 2007-02337offer some description of attempting to improve the brittleness of Bbased on additives, the method is not very clear. Japanese PatentApplication Publication Nos. 2006-4611 and 2007-02337 merely propose theforegoing compositions, and do not disclose a specific productionmethod. Moreover, Japanese Patent Application Publication Nos. 2006-4611and 2007-02337 do not describe the problem of cracks in the B-rich phaseand the solution thereof.

Japanese Patent Application Publication No. 2008-23545 discloses asputtering target having a fine and uniform structure by improving thecasting process and improving the rolling process of a Co—Cr—Pt—B-basedalloy. As the specific processes to be perfoiined after casting, theingot is subject to hot rolling at a rolling reduction of 1.33% andtemperature of 1100° C. for each pass, and rolling is performed 48 timesfor causing the crystal grain size of the alloy to be 100 μm or less.The rolling rate in the foregoing case is 55% (rolling rate is roughly45% to 65%). Nevertheless, Japanese Patent Application Publication No.2008-23545 does not describe the problem of cracks in the B-rich phaseand the solution thereof.

Japanese Patent Application Publication No. H6-41735 describes producinga Cr—B target member as a sintered compact. Moreover, Japanese PatentApplication Publication No. H6-41735 describes that, since the hard andbrittle Cr—B intermetallic compound cracks easily and cannot be subjectto plastic working, it is possible to produce a high-density target,which is desirable as a target member, by producing the target member asa sintered compact. Nevertheless, Japanese Patent ApplicationPublication No. H6-41735 does not describe the problem of cracks in theB-rich phase and the solution thereof.

International Publication No. 2005/093124 discloses a Co—Cr—Pt—B-basedalloy sputtering target comprising an island-shaped rolled structuremade from a Co-rich phase based on the primary crystals during casting,wherein the hot rolling rate is set to 15% to 40%. Moreover,International Publication No. 2005/093124 describes that, when the hotrolling rate is less than 15%, the dendritic structure cannot bedestroyed, and segregation and residual stress cannot be sufficientlyeliminated, and when the hot rolling rate exceeds 40%, the Co-rich phaseand the B-rich phase become coarse when the processes of rolling andheat treatment are repeated. Nevertheless, International Publication No.2005/093124 does not describe the problem of cracks in the B-rich phaseand the solution thereof.

International Publication No. 2011/070860 describes a sputtering targetcontaining B obtained via melting and casting, wherein the B content is10 at % to 50 at %, remainder is one type among Co, Fe, and Ni, and theoxygen content is 100 wtppm or less. The object of this technology is toachieve a higher density in comparison to conventional powder sinteredcompact targets by considerably reducing the oxygen content.Nevertheless, International Publication No. 2011/070860 does notdescribe the problem of cracks in the B-rich phase and the solutionthereof.

SUMMARY

As described above, when the Co—Pt—B-based alloy or the like is subjectto cold rolling, there is a problem in that the brittle B-rich phase inthe alloy is subject to brittle fracture, and cracks are generated. Inaddition, there is a problem in that the cracked B-rich phase becomesthe source of arcing during the sputtering process and causes thegeneration of particles. In order to resolve this problem, consideredmay be producing the target without performing cold rolling.Nevertheless, since it is not possible to introduce strain into thetarget structure if cold rolling is not performed, there is a problem inthat the leakage flux density cannot be increased.

In order to resolve the foregoing problems, as a result of intensestudy, the present inventors discovered that the stress concentration ofthe B-rich phase can be reduced by intentionally cracking the B-richphase and separating the refined phase, and cracks in the B-rich phaseduring the cold rolling process can thereby be reduced.

Based on the foregoing discovery, the present invention provides: asputtering target for a magnetic recording medium, wherein an averagegrain area of a B-rich phase is 90 μm² or less. The sputtering targetmay be made from 1 to 26 at % of Pt, 1 to 15 at % of B, and remainderbeing Co and unavoidable impurities, 1 to 40 at % of Cr, 1 to 26 at % ofPt, 1 to 15 at % of B, and remainder being Co and unavoidableimpurities, or 1 to 40 at % of Cr, 1 to 15 at % of B, and remainderbeing Co and unavoidable impurities. Any of the above referencedsputtering targets may contain one or more elements selected from Cu,Ru, Ta, and Nd in an amount of 1 at % or more and 10 at % or less. Thenumber of cracks in a B-rich phase of the sputtering target may be 2500cracks/mm², and a maximum magnetic permeability (μ_(max)) of thesputtering target may be 50 or less.

The present invention also provides a process for producing a sputteringtarget for a magnetic recording medium, wherein an alloy cast ingot issubject to heat treatment, thereafter subject to primary rolling whichincludes at least one pass of cold rolling, thereafter subject tosecondary rolling, and machined to prepare a target. The primary rollingmay be performed at a total rolling reduction of 10 to 90%, and thesecondary rolling may be performed at a total rolling reduction of 1.0to 10%. The process may be used to produce any of the above referencedsputtering targets.

The present invention yields a superior effect of being able to providea sputtering target for a magnetic recording medium that has few cracksin the B-rich phase and has a high leakage flux density. It is therebypossible to stabilize the discharge during sputtering, suppress arcingwhich occurs from cracks in the B-rich phase, and effectively prevent orsuppress the generation of nodules or particles. Moreover, the presentinvention yields a superior effect of being able to form a high-qualityfilm and considerably improve the production yield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of the target of Example 1 and shows arepresentative example where the B-rich phase is finely separated(surface that is parallel to the sputtering surface; the lower diagramis an enlarged view of the upper diagram).

FIG. 2 is a photograph of the target of Example 2 and shows arepresentative example where the B-rich phase is finely separated(surface that is parallel to the sputtering surface; the lower diagramis an enlarged view of the upper diagram).

FIG. 3 is a photograph of the target of Example 4 and shows arepresentative example where the B-rich phase is finely separated(surface that is parallel to the sputtering surface; the lower diagramis an enlarged view of the upper diagram).

FIG. 4 is a photograph of the target of Comparative Example 1 and showsa representative example where the B-rich phase exists in a large state(surface that is parallel to the sputtering surface; the lower diagramis an enlarged view of the upper diagram).

FIG. 5 is a photograph of the target of Comparative Example 2 and showsa representative example where the B-rich phase exists in a large state(surface that is parallel to the sputtering surface; the lower diagramis an enlarged view of the upper diagram).

FIG. 6 is a photograph of the target of Comparative Example 1 and showsthe cracks in the B-rich phase.

DETAILED DESCRIPTION

The present invention provides a sputtering target for a magneticrecording medium in which the average grain area of the B-rich phase is90 μm² or less. The term “B-rich phase” referred to herein is an areacontaining more B than the peripheral area (matrix), and the area isseparated into a matrix phase and a B-rich phase. While the shape andamount of the B-rich phase will change depending on the additive amountof B relative to the other metals of the alloy system, the B-rich phaseoften has a shape like cirrocumulus clouds (mackerel clouds, altocumulusclouds) as shown in FIG. 1 and FIG. 2 in the matrix.

When the grain area of the B-rich phase is large, the stressconcentration during the cold rolling process will increase and,therefore, the strength will deteriorate and cracks in the B-rich phasewill increase. Thus, as described later, by intentionally cracking theB-rich phase via cold rolling and finely separating the cracked B-richphase via hot rolling, the grain area of the B-rich phase is reduced.Consequently, the B-rich phase will not crack easily even uponsubsequently performing the cold rolling process for increasing theleakage flux density.

In the present invention, by causing the average grain area of theB-rich phase to be 90 μm² or less, it is possible to sufficientlyprevent cracks in the B-rich phase caused by cold rolling. Specifically,the number of cracks in the B-rich phase in a 1 mm×1 mm area (visualfield) is preferably 2500 cracks or less. It is thereby possible toeffectively suppress the generation of arcing during sputtering.

The sputtering target for a magnetic recording medium of the presentinvention is configured from a Co—Pt—B-based alloy, a Co—Cr—Pt—B-basedalloy or a Co—Cr—B-based alloy. While there is no limitation in thecomponent composition of these alloys so as long as it is publicly knownfor use as a magnetic recording medium, preferably used is aCo—Pt—B-based alloy made from 1 to 26 at % of Pt, 1 to 15 at % of B, andremainder being Co and unavoidable impurities, preferably used is aCo—Cr—Pt—B-based alloy made from 1 to 40 at % of Cr, 1 to 26 at % of Pt,1 to 15 at % of B, and remainder being Co and unavoidable impurities,and preferably used is a Co—Cr—B-based alloy made from 1 to 40 at % ofCr, 1 to 15 at % of B, and remainder being Co and unavoidableimpurities.

In addition, in the present invention, one or more elements selectedfrom Cu, Ru, Ta, and Nd may be added as additive elements in an amountof 1 at % or more and 10 at % or less in order to increase the leakageflux density.

The leakage flux density has a correlation with the maximum magneticpermeability. In other words, the leakage flux density will be higher asthe maximum magnetic permeability is lower. In the present invention,when the maximum magnetic permeability is 50 or less, it is possible toobtain sufficient leakage flux density that will not cause an abnormaldischarge.

As an effective means for increasing the leakage flux density, straincan be added to an alloy sheet for a magnetic recording medium via coldrolling, but when cold rolling is performed in a state where the area ofthe B-rich phase is large, the generation of cracks in the B-rich phasewill increase. Thus, the focus of the present invention is to finelyseparate the B-rich phase before the cold rolling process as describedabove. It could be said that the technique for finely separating theB-rich phase did not conventionally exist. By finely refining the B-richphase as described above, the number of cracks in the B-rich phase canbe made to be 2500 cracks/mm².

The sputtering target for a magnetic recording medium of the presentinvention can be produced, for example, according to the followingmethod.

Foremost, an alloy ingot based on Co—Pt—B or the like obtained viacasting is subject to primary rolling which includes at least one passof cold rolling. As primary rolling which includes at least one pass ofcold rolling, there are, for example, the following combinations: 1) hotrolling-cold rolling-hot rolling; 2) hot rolling-cold rolling-hotrolling-hot rolling; 3) hot rolling-hot rolling-cold rolling-coldrolling-hot rolling; and so on.

There is no particular limitation on the number of times that rolling isperformed, and so as long as the total rolling reduction is 10 to 90%,the number of times that rolling is performed may be suitably decidedaccording to the intended thickness. Moreover, while there is noparticular rule regarding order of rolling; for example, coldrolling→hot rolling, hot rolling→hot rolling, when a cast ingot obtainedvia casting is subject to cold rolling, there are cases where the ingotitself becomes cracked from the defects that were generated during thecasting process. Thus, in order to remove such defects to a certainextent, hot rolling is preferably performed as the initial rollingprocess.

In the present invention, the total rolling reduction of cold rolling inthe primary rolling is preferably set to 1% or more, and causing thetotal rolling reduction of hot rolling in the primary rolling to be 30%or more is extremely effective in separating the B-rich phase. Note thatthe term “total rolling reduction” as used herein refers to the totaldecreasing rate of the material thickness.

Subsequently, in order to increase the leakage flux density, secondaryrolling is performed for the purpose of introducing strain into thestructure. Secondary rolling is performed by repeating the cold rollingprocess. There is no particular limitation on the number of times thatrolling is performed, and so as long as the total rolling reduction is0.1 to 10%, the number of times that rolling is performed may besuitably decided according to the intended thickness and the intendedleakage flux density. However, when the percentage content of Cr ishigh, it is not necessary to perform secondary rolling since themagnetic permeability will be low.

Conventionally, cracks would sometimes be generated in the B-rich phasedue to the rolling that is performed for increasing the leakage fluxdensity. Meanwhile, the leakage flux density was reduced as a measurefor preventing the foregoing cracks, and the cracks in the B-rich phasewere prevented by lowering the total rolling reduction during thesecondary rolling process. Nevertheless, since the present invention cansuppress the cracks in the B-rich phase by finely separating the B-richphase in the alloy by performing primary rolling, which includes atleast one pass of cold rolling, prior to performing secondary rolling,the present invention yields an extremely advantageous effect of nothaving to sacrifice the leakage flux density as with conventionaltechnologies.

By cutting the rolled ingot obtained as described above into an intendedshape and polishing the surface thereof, it is possible to produce thesputtering target for a magnetic recording medium of the presentinvention. The sputtering target for a magnetic recording mediumproduced as described above can cause the average grain area of theB-rich phase to be 90 μm² and is effective for causing the number ofcracks in the B-rich phase to be 2500 cracks/mm² and preventing thegeneration of particles.

EXAMPLES

The present invention is now explained based on the Examples andComparative Examples. Note that these Examples are merely illustrative,and the present invention is not in any way limited by these Examples.In other words, the present invention is limited only by the scope ofclaims and covers the various modifications other than the Examplesincluded in this invention.

Example 1

A Co—Cr—Pt—B alloy raw material made from 15 at % of Cr, 14.5 at % ofPt, 8 at % of B, and remainder being Co and unavoidable impurities wassubject to radio frequency (vacuum) melting. The resulting product wascast using a mold, which is configured by cobalt being set on a coppersurface plate, at a temperature between melting point and melting point+100° C. to obtain an ingot of 180×300×33t.

Subsequently, the obtained ingot was subject to primary rolling at atotal rolling reduction of 62%. Here, the annealing temperature duringthe hot rolling was set to 1090° C. Subsequently, the obtained rolledmaterial was subject to secondary rolling at a total rolling reductionof 5.0%. The resulting product was machined to obtain a target.

The surface parallel to the sputtering surface of this target wasobserved at ten arbitrary visual fields (areas) of 190 μm×240 μm usingan FE-EPMA (model number: JXA-8500F) electron microscope manufactured byJEOL. Consequently, the average grain area of the B-rich phase was 77.7μm². Moreover, the number of cracks in the B-rich phase was counted and,as a result of obtaining the average value thereof and normalizing thesame, the number of cracks in the B-rich phase was 1600 cracks/mm². Inaddition, as a result of measuring the maximum magnetic permeability(μ_(max)) in the horizontal direction relative to the sputtering surfaceof this target using a B—H meter (BHU-6020) manufactured by RikenDenshi, the maximum magnetic permeability (μ_(max)) was 8.3.

TABLE 1 Heat Treatment Total Rolling Total Rolling Average Grain MaximumTarget (Annealing) Reduction of Reduction of Area of B-rich Cracks ofB-rich Magnetic Composition Ratio Temperature Primary Secondary RollingPhase Phase Permeability (at. %) (° C.) Rolling (%) (%) (μm²)(crack/mm²) (μmax) Example 1 Co—15Cr—14.5Pt—8B 1090 62 5.0% 77.7 16008.3 Example 2 Co—15Cr—17.5Pt—8B 1090 86 4.2% 44.6 1500 8.3 Example 3Co—15Cr—11Pt—12B 1100 73 3.6% 84.9 2000 11 Example 4 Co—14.5Cr—17Pt—8B1000 68 5.2% 75.1 1100 8.9 Example 5 Co—14Cr—15.5Pt—10B 1100 65 4.8%83.5 1900 11.8 Example 6 Co—14Cr—14Pt—6B 800 80 3.2% 74.3 900 10.6Example 7 Co—15Cr—17.5Pt—7B 900 78 3.9% 50.1 1200 9.2 Example 8Co—16Cr—17.5Pt—7B 900 66 2.2% 44.3 1100 7.7 Example 9 Co—17Cr—15.5Pt—9B1000 73 1.2% 71.5 1500 9 Example 10 Co—14.5Cr—15Pt—7B 1100 74 4.3% 75.21400 10.1 Example 11 Co—10Cr—16Pt—2B 700 76 4.1% 30 10 10.8 Example 12Co—20Cr—18Pt—2B 800 70 4.9% 42.6 200 5.7 Example 13 Co—15Cr—21.5Pt—8B1100 61 2.1% 84.7 2100 8 Example 14 Co—6Cr—18.5Pt—2B 1100 73 3.6% 20.150 18.4 Example 15 Co—26Cr—13Pt—7B 900 50 1.1% 90 1400 0.3 Example 16Co—1Cr—13.5Pt—7B 900 67 2.9% 78.9 1400 38.7 Example 17 Co—22.5Pt—7B 110077 3.8% 81.5 2100 39.5 Example 18 Co—4Cr—18Pt—6B—5Cu 1070 69 4.4% 58.91000 25.9 Example 19 Co—4Cr—18Pt—6B—0.5Cu 1070 72 2.6% 61.3 1100 29.7Example 20 Co—15Cr—5Pt—5B—5Ru 1100 80 6.0% 75.6 1500 6.8 Example 21Co—10Cr—12Pt—5B—1Ru 1090 73 9.0% 77.2 1400 12.5 Example 22Co—12Cr—14Pt—6B—10Ru 1100 76 1.6% 80.1 1800 10.6 Example 23Co—15Cr—8B—2Ta 1100 72 2.9% 87.6 2200 8.3 Example 24Co—15Cr—12.5Pt—6B—1Ta 1100 66 3.5% 80.2 1300 7.7 Example 25Co—20Cr—11Pt—4B—1Nd 1100 10 1.0% 88.6 1200 3.4 Example 26Co—10Cr—25Pt—5B 1100 72 3.3% 64.6 1300 9.8 Example 27 Co—10Cr—18Pt—15B1100 73 3.5% 89.7 2500 10.5 Example 28 Co—40Cr—10Pt—1B 1100 69 0.0% 30.5100 0.2 Example 29 Co—10Cr—1Pt—5B 1080 71 4.6% 68.9 1400 11.6 Example 30Co—10Cr—30Pt—5B 1100 70 2.8% 78.9 1100 10.8 Example 31 Co—10Cr—16Pt—2B1090 72 10.0% 25 200 7.8 Example 32 Co—13Cr—8Pt—4B 1090 75 2.5% 76.8 80015.9 Comparative Co—15Cr—14.5Pt—8B 1090 62 4.8% 111.7 4800 8.2 Example 1Comparative Co—15Cr—17.5Pt—8B 1090 72 4.1% 112.4 4700 8.4 Example 2Comparative Co—15Cr—11Pt—12B 1100 71 3.3% 182.7 5300 11.1 Example 3Comparative Co—14.5Cr—17Pt—8B 1000 69 5.2% 113.6 4800 9.3 Example 4Comparative Co—14Cr—15.5Pt—10B 1100 60 4.8% 195.2 5200 11.5 Example 5Comparative Co—14Cr—14Pt—6B 800 75 3.1% 118.7 4200 10.8 Example 6Comparative Co—15Cr—17.5Pt—7B 900 79 3.9% 98.7 4400 9.1 Example 7Comparative Co—16Cr—17.5Pt—7B 900 53 2.0% 93.9 4300 7.8 Example 8Comparative Co—17Cr—15.5Pt—9B 1000 76 1.2% 111.2 5000 8.8 Example 9Comparative Co—14.5Cr—15Pt—7B 1100 72 4.2% 107.5 4200 10.2 Example 10Comparative Co—10Cr—16Pt—2B 700 69 3.8% 92.6 2600 10.4 Example 11Comparative Co—20Cr—18Pt—2B 800 71 4.9% 94.3 2600 6.1 Example 12Comparative Co—15Cr—21.5Pt—8B 1100 64 2.1% 151.2 5100 7.8 Example 13Comparative Co—6Cr—18.5Pt—2B 1100 72 3.6% 91.6 2700 17.8 Example 14Comparative Co—26Cr—13Pt—7B 900 50 1.0% 143.3 4500 0.4 Example 15Comparative Co—1Cr—13.5Pt—7B 900 69 2.7% 102.3 5500 38.9 Example 16Comparative Co—22.5Pt—7B 1100 74 3.5% 120.2 3900 39.7 Example 17Comparative Co—4Cr—18Pt—6B—5Cu 1070 70 4.3% 92.4 2600 27.6 Example 18Comparative Co—4Cr—18Pt—6B—0.5Cu 1070 66 2.6% 93.1 2700 28.8 Example 19Comparative Co—15Cr—5Pt—5B—5Ru 1100 82 5.8% 94.5 2700 8.9 Example 20Comparative Co—10Cr—12Pt—5B—1Ru 1090 71 9.0% 96.9 2900 12.3 Example 21Comparative Co—12Cr—14Pt—6B—10Ru 1100 76 1.5% 98.8 3000 10.5 Example 22Comparative Co—15Cr—8B—2Ta 1100 70 2.9% 103.4 4500 8 Example 23Comparative Co—15Cr—12.5Pt—6B—1Ta 1100 69 3.5% 97.9 3700 7.8 Example 24Comparative Co—20Cr—11Pt—4B—1Nd 1100 11 1.0% 120.1 3200 3.2 Example 25Comparative Co—10Cr—25Pt—5B 1100 67 3.0% 94.8 3000 10.1 Example 26Comparative Co—10Cr—18Pt—15B 1100 63 3.4% 162.3 5300 9.7 Example 27Comparative Co—40Cr—10Pt—1B 1100 74 0.0% 91.2 2600 0.2 Example 28Comparative Co—10Cr—1Pt—5B 1080 73 4.5% 100.3 2700 11.8 Example 29Comparative Co—10Cr—30Pt—5B 1100 69 2.8% 106.7 2900 10.9 Example 30Comparative Co—13Cr—8Pt—4B 1090 75 0.0% 92.6 120 51.2 Example 31

Example 2

As shown in Table 1, the composition ratio was set to Co-15Cr-17.5Pt-8B,and a target was produced according to the same production process asExample 1. Here, the ingot size after casting was 180×300×36t. Moreover,the annealing temperature was set to 1090° C., the total rollingreduction of the primary rolling was set to 86%, and the total rollingreduction of the secondary rolling was set to 4.2%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 44.6μm², and the number of cracks in the B-rich phase was 1500 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 8.3.

Example 3

As shown in Table 1, the composition ratio was set to Co-15Cr-11Pt-12B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 73%, and thetotal rolling reduction of the secondary rolling was set to 3.6%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 84.9μm², and the number of cracks in the B-rich phase was 2000 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 11.

Example 4

As shown in Table 1, the composition ratio was set to Co-14.5Cr-17Pt-8B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1000° C., thetotal rolling reduction of the primary rolling was set to 68%, and thetotal rolling reduction of the secondary rolling was set to 5.2%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 75.1μm², and the number of cracks in the B-rich phase was 1100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 8.9.

Example 5

As shown in Table 1, the composition ratio was set toCo-14Cr-15.5Pt-10B, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1100° C., the total rolling reduction of the primary rolling was setto 65%, and the total rolling reduction of the secondary rolling was setto 4.8%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 83.5μm², and the number of cracks in the B-rich phase was 1900 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 11.8.

Example 6

As shown in Table 1, the composition ratio was set to Co-14Cr-14Pt-6B,and a target was produced according to the same production process asExample 1. Here, the ingot size after casting was 180×300×36t. Moreover,the annealing temperature was set to 800° C., the total rollingreduction of the primary rolling was set to 80%, and the total rollingreduction of the secondary rolling was set to 3.2%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 74.3μm², and the number of cracks in the B-rich phase was 900 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.6.

Example 7

As shown in Table 1, the composition ratio was set to Co-15Cr-17.5Pt-7B,and a target was produced according to the same production process asExample 1. Here, the ingot size after casting was 180×300×36t. Moreover,the annealing temperature was set to 900° C., the total rollingreduction of the primary rolling was set to 78%, and the total rollingreduction of the secondary rolling was set to 3.9%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 50.1μm², and the number of cracks in the B-rich phase was 1200 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 9.2.

Example 8

As shown in Table 1, the composition ratio was set to Co-16Cr-17.5Pt-7B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 900° C., the totalrolling reduction of the primary rolling was set to 66%, and the totalrolling reduction of the secondary rolling was set to 2.2%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 44.3μm², and the number of cracks in the B-rich phase was 1100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 7.7.

Example 9

As shown in Table 1, the composition ratio was set to Co-17Cr-15.5Pt-9B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1000° C., thetotal rolling reduction of the primary rolling was set to 73%, and thetotal rolling reduction of the secondary rolling was set to 1.2%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 71.5μm², and the number of cracks in the B-rich phase was 1500 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 9.

Example 10

As shown in Table 1, the composition ratio was set to Co-14.5Cr-15Pt-7B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 74%, and thetotal rolling reduction of the secondary rolling was set to 4.3%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 75.2μm², and the number of cracks in the B-rich phase was 1400 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.1.

Example 11

As shown in Table 1, the composition ratio was set to Co-10Cr-16Pt-2B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 700° C., the totalrolling reduction of the primary rolling was set to 76%, and the totalrolling reduction of the secondary rolling was set to 4.1%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 30.0μm², and the number of cracks in the B-rich phase was 10 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.8.

Example 12

As shown in Table 1, the composition ratio was set to Co-20Cr-18Pt-2B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 800° C., the totalrolling reduction of the primary rolling was set to 70%, and the totalrolling reduction of the secondary rolling was set to 4.9%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 42.6μm², and the number of cracks in the B-rich phase was 200 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 5.7.

Example 13

As shown in Table 1, the composition ratio was set to Co-15Cr-21.5Pt-8B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 61%, and thetotal rolling reduction of the secondary rolling was set to 2.1%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 84.7μm², and the number of cracks in the B-rich phase was 2100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 8.

Example 14

As shown in Table 1, the composition ratio was set to Co-6Cr-18.5Pt-2B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 73%, and thetotal rolling reduction of the secondary rolling was set to 3.6%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 20.1μm², and the number of cracks in the B-rich phase was 50 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 18.4.

Example 15

As shown in Table 1, the composition ratio was set to Co-26Cr-13Pt-7B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 900° C., the totalrolling reduction of the primary rolling was set to 50%, and the totalrolling reduction of the secondary rolling was set to 1.1%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 90.0μm², and the number of cracks in the B-rich phase was 1400 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 0.3.

Example 16

As shown in Table 1, the composition ratio was set to Co-1Cr-13.5Pt-7B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 900° C., the totalrolling reduction of the primary rolling was set to 67%, and the totalrolling reduction of the secondary rolling was set to 2.9%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 78.9μm², and the number of cracks in the B-rich phase was 1400 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 38.7.

Example 17

As shown in Table 1, the composition ratio was set to Co-22.5Pt-7B, anda target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 77%, and thetotal rolling reduction of the secondary rolling was set to 3.8%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 81.5μm², and the number of cracks in the B-rich phase was 2100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 39.5.

Example 18

As shown in Table 1, the composition ratio was set toCo-4Cr-18Pt-6B-5Cu, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1070° C., the total rolling reduction of the primary rolling was setto 69%, and the total rolling reduction of the secondary rolling was setto 4.4%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 58.9μm², and the number of cracks in the B-rich phase was 1000 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 25.9.

Example 19

As shown in Table 1, the composition ratio was set toCo-4Cr-18Pt-6B-0.5Cu, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1070° C., the total rolling reduction of the primary rolling was setto 72%, and the total rolling reduction of the secondary rolling was setto 2.6%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 61.3μm², and the number of cracks in the B-rich phase was 1100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 29.7.

Example 20

As shown in Table 1, the composition ratio was set toCo-15Cr-5Pt-5B-5Ru, and a target was produced according to the sameproduction process as Example 1. Here, the ingot size after casting was180×300×36t. Moreover, the annealing temperature was set to 1100° C.,the total rolling reduction of the primary rolling was set to 80%, andthe total rolling reduction of the secondary rolling was set to 6.0%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 75.6μm², and the number of cracks in the B-rich phase was 1500 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 6.8.

Example 21

As shown in Table 1, the composition ratio was set toCo-10Cr-12Pt-5B-1Ru, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1090° C., the total rolling reduction of the primary rolling was setto 73%, and the total rolling reduction of the secondary rolling was setto 9.0%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 77.2μm², and the number of cracks in the B-rich phase was 1400 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 12.5.

Example 22

As shown in Table 1, the composition ratio was set toCo-12Cr-14Pt-6B-10Ru, and a target was produced according to the sameproduction process as Example 1. Here, the ingot size after casting was180×300×36t. Moreover, the annealing temperature was set to 1100° C.,the total rolling reduction of the primary rolling was set to 76%, andthe total rolling reduction of the secondary rolling was set to 1.6%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 80.1μm², and the number of cracks in the B-rich phase was 1800 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.6.

Example 23

As shown in Table 1, the composition ratio was set to Co-15Cr-8B-2Ta,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 72%, and thetotal rolling reduction of the secondary rolling was set to 2.9%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 87.6μm², and the number of cracks in the B-rich phase was 2200 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 8.3.

Example 24

As shown in Table 1, the composition ratio was set toCo-15Cr-12.5Pt-6B-1Ta, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1100° C., the total rolling reduction of the primary rolling was setto 66%, and the total rolling reduction of the secondary rolling was setto 3.5%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 80.2μm², and the number of cracks in the B-rich phase was 1300 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 7.7.

Example 25

As shown in Table 1, the composition ratio was set toCo-20Cr-11Pt-4B-1Nd, and a target was produced according to the sameproduction process as Example 1. Here, the annealing temperature was setto 1100° C., the total rolling reduction of the primary rolling was setto 10%, and the total rolling reduction of the secondary rolling was setto 1.0%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 88.6μm², and the number of cracks in the B-rich phase was 1200 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 3.4.

Example 26

As shown in Table 1, the composition ratio was set to Co-10Cr-25Pt-5B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 72%, and thetotal rolling reduction of the secondary rolling was set to 3.3%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 64.6μm², and the number of cracks in the B-rich phase was 1300 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 9.8.

Example 27

As shown in Table 1, the composition ratio was set to Co-10Cr-18Pt-15B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 73%, and thetotal rolling reduction of the secondary rolling was set to 3.5%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 89.7μm², and the number of cracks in the B-rich phase was 2500 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.5.

Example 28

As shown in Table 1, the composition ratio was set to Co-40Cr-10Pt-1B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 69%, and thetotal rolling reduction of the secondary rolling was set to 0.0%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 30.5μm², and the number of cracks in the B-rich phase was 100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 0.2. While the secondary rollingwas not performed in this Example, a sufficiently low magneticpermeability was obtained since the percentage content of Cr was high.

Example 29

As shown in Table 1, the composition ratio was set to Co-10Cr-1Pt-5B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1080° C., thetotal rolling reduction of the primary rolling was set to 71%, and thetotal rolling reduction of the secondary rolling was set to 4.6%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 68.9μm², and the number of cracks in the B-rich phase was 1400 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 11.6.

Example 30

As shown in Table 1, the composition ratio was set to Co-10Cr-30Pt-5B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1100° C., thetotal rolling reduction of the primary rolling was set to 70%, and thetotal rolling reduction of the secondary rolling was set to 2.8%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 78.9μm², and the number of cracks in the B-rich phase was 1100 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 10.8.

Example 31

As shown in Table 1, the composition ratio was set to Co-10Cr-16Pt-2B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1090° C., thetotal rolling reduction of the primary rolling was set to 72%, and thetotal rolling reduction of the secondary rolling was set to 10.0%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 25.0μm², and the number of cracks in the B-rich phase was 200 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 7.8.

Example 32

As shown in Table 1, the composition ratio was set to Co-13Cr-8Pt-4B,and a target was produced according to the same production process asExample 1. Here, the annealing temperature was set to 1090° C., thetotal rolling reduction of the primary rolling was set to 75%, and thetotal rolling reduction of the secondary rolling was set to 2.5%.

As a result of analyzing this target with the same method as Example 1,as shown in Table 1, the average grain area of the B-rich phase was 76.8μm², and the number of cracks in the B-rich phase was 800 cracks/mm².Moreover, the maximum magnetic permeability in the horizontal directionrelative to the sputtering surface was 15.9.

In all of the Example, it was confirmed that the average grain area ofthe B-rich phase was 90 μm² or less and finely separated. When theB-rich phase is finely separated as described above, it was confirmedthat the cracks in the B-rich phase could be suppressed to 2500cracks/mm². Moreover, the maximum magnetic permeability (μ_(max)) in theforegoing case was 50 or less. This kind of structure plays an extremelyimportant role in order to suppress the amount of particles that aregenerated during sputtering and improve the yield during deposition.

Comparative Example 1

A Co—Cr—Pt—B alloy raw material made from 15 at % of Cr, 14.5 at % ofPt, 8 at % of B, and remainder being Co and unavoidable impurities wassubject to radio frequency (vacuum) melting. The resulting product wascast using a mold, which is configured by cobalt being set on a coppersurface plate, at a temperature between melting point and melting point+100° C. to obtain an ingot of 200×300×30t.

Subsequently, the obtained ingot was subject to heat treatment at 1090°C., and thereafter subject to primary rolling at a total rollingreduction of 62%. In Comparative Example 1 and Comparative Examples 2 to31 described later, hot rolling was performed as the primary rolling inall cases. Subsequently, the obtained rolled material was subject tosecondary rolling at a total rolling reduction of 4.8%. The resultingproduct was machined to obtain a target.

The surface parallel to the sputtering surface of this target wasobserved at ten arbitrary visual fields (areas) of 190 μm×240 μm usingan FE-EPMA (model number: JXA-8500F) electron microscope manufactured byJEOL. Consequently, the average grain area of the B-rich phase was 111.7μm². Moreover, the number of cracks in the B-rich phase was counted and,as a result of obtaining the average value thereof and normalizing thesame, the number of cracks in the B-rich phase was 4800 cracks/mm². Inaddition, as a result of measuring the maximum magnetic permeability(μ_(max)) in the horizontal direction relative to the sputtering surfaceof this target using a B—H meter (BHU-6020) manufactured by RikenDenshi, the maximum magnetic permeability (μ_(max)) was 8.2.

Comparative Example 2

As shown in Table 1, the composition ratio was set to Co-15Cr-17.5Pt-8B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1090°C., the total rolling reduction of the primary rolling was set to 72%,and the total rolling reduction of the secondary rolling was set to4.1%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 112.4 μm², and the number of cracks in the B-rich phase was4700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 8.4.

Comparative Example 3

As shown in Table 1, the composition ratio was set to Co-15Cr-11Pt-12B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 71%,and the total rolling reduction of the secondary rolling was set to3.3%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 182.7 μm², and the number of cracks in the B-rich phase was5300 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 11.1.

Comparative Example 4

As shown in Table 1, the composition ratio was set to Co-14.5Cr-17Pt-8B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1000°C., the total rolling reduction of the primary rolling was set to 69%,and the total rolling reduction of the secondary rolling was set to5.2%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 113.6 μm², and the number of cracks in the B-rich phase was4800 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 9.3.

Comparative Example 5

As shown in Table 1, the composition ratio was set toCo-14Cr-15.5Pt-10B, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1100° C., the total rolling reduction of theprimary rolling was set to 60%, and the total rolling reduction of thesecondary rolling was set to 4.8%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 195.2 μm², and the number of cracks in the B-rich phase was5200 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 11.5.

Comparative Example 6

As shown in Table 1, the composition ratio was set to Co-14Cr-14Pt-6B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 800°C., the total rolling reduction of the primary rolling was set to 75%,and the total rolling reduction of the secondary rolling was set to3.1%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 118.7 μm², and the number of cracks in the B-rich phase was4200 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.8.

Comparative Example 7

As shown in Table 1, the composition ratio was set to Co-15Cr-17.5Pt-7B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 900°C., the total rolling reduction of the primary rolling was set to 79%,and the total rolling reduction of the secondary rolling was set to3.9%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 98.7 m², and the number of cracks in the B-rich phase was 4400cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 9.1.

Comparative Example 8

As shown in Table 1, the composition ratio was set to Co-16Cr-17.5Pt-7B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 900°C., the total rolling reduction of the primary rolling was set to 53%,and the total rolling reduction of the secondary rolling was set to2.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 93.9 μm², and the number of cracks in the B-rich phase was4300 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 7.8.

Comparative Example 9

As shown in Table 1, the composition ratio was set to Co-17Cr-15.5Pt-9B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1000°C., the total rolling reduction of the primary rolling was set to 76%,and the total rolling reduction of the secondary rolling was set to1.2%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 111.2 μm², and the number of cracks in the B-rich phase was5000 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 8.8.

Comparative Example 10

As shown in Table 1, the composition ratio was set to Co-14.5Cr-15Pt-7B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 72%,and the total rolling reduction of the secondary rolling was set to4.2%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 107.5 μm², and the number of cracks in the B-rich phase was4200 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.2.

Comparative Example 11

As shown in Table 1, the composition ratio was set to Co-10Cr-16Pt-2B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 700°C., the total rolling reduction of the primary rolling was set to 69%,and the total rolling reduction of the secondary rolling was set to3.8%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 92.6 μm², and the number of cracks in the B-rich phase was2600 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.4.

Comparative Example 12

As shown in Table 1, the composition ratio was set to Co-20Cr-18Pt-2B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 800°C., the total rolling reduction of the primary rolling was set to 71%,and the total rolling reduction of the secondary rolling was set to4.9%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 94.3 μm², and the number of cracks in the B-rich phase was2600 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 6.1.

Comparative Example 13

As shown in Table 1, the composition ratio was set to Co-15Cr-21.5Pt-8B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 64%,and the total rolling reduction of the secondary rolling was set to2.1%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 151.2 μm², and the number of cracks in the B-rich phase was5100 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 7.8.

Comparative Example 14

As shown in Table 1, the composition ratio was set to Co-6Cr-18.5Pt-2B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 72%,and the total rolling reduction of the secondary rolling was set to3.6%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 91.6 μm², and the number of cracks in the B-rich phase was2700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 17.8.

Comparative Example 15

As shown in Table 1, the composition ratio was set to Co-26Cr-13Pt-7B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 900°C., the total rolling reduction of the primary rolling was set to 50%,and the total rolling reduction of the secondary rolling was set to1.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 143.3 μm², and the number of cracks in the B-rich phase was4500 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 0.4.

Comparative Example 16

As shown in Table 1, the composition ratio was set to Co-1Cr-13.5Pt-7B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 900°C., the total rolling reduction of the primary rolling was set to 69%,and the total rolling reduction of the secondary rolling was set to2.7%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 102.3 μm², and the number of cracks in the B-rich phase was5500 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 38.9.

Comparative Example 17

As shown in Table 1, the composition ratio was set to Co-22.5Pt-7B, anda target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 74%,and the total rolling reduction of the secondary rolling was set to3.5%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 120.2 μm², and the number of cracks in the B-rich phase was3900 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 39.7.

Comparative Example 18

As shown in Table 1, the composition ratio was set toCo-4Cr-18Pt-6B-5Cu, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1070° C., the total rolling reduction of theprimary rolling was set to 70%, and the total rolling reduction of thesecondary rolling was set to 4.3%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 92.4 m², and the number of cracks in the B-rich phase was 2600cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 27.6.

Comparative Example 19

As shown in Table 1, the composition ratio was set toCo-4Cr-18Pt-6B-0.5Cu, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1070° C., the total rolling reduction of theprimary rolling was set to 66%, and the total rolling reduction of thesecondary rolling was set to 2.6%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 93.1 μm², and the number of cracks in the B-rich phase was2700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 28.8.

Comparative Example 20

As shown in Table 1, the composition ratio was set toCo-15Cr-5Pt-5B-5Ru, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1100° C., the total rolling reduction of theprimary rolling was set to 82%, and the total rolling reduction of thesecondary rolling was set to 5.8%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 94.5 μm², and the number of cracks in the B-rich phase was2700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 8.9.

Comparative Example 21

As shown in Table 1, the composition ratio was set toCo-10Cr-12Pt-5B-1Ru, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1090° C., the total rolling reduction of theprimary rolling was set to 71%, and the total rolling reduction of thesecondary rolling was set to 9.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 96.9 μm², and the number of cracks in the B-rich phase was2900 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 12.3.

Comparative Example 22

As shown in Table 1, the composition ratio was set toCo-12Cr-14Pt-6B-10Ru, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1100° C., the total rolling reduction of theprimary rolling was set to 76%, and the total rolling reduction of thesecondary rolling was set to 1.5%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 98.8 μm², and the number of cracks in the B-rich phase was3000 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.5.

Comparative Example 23

As shown in Table 1, the composition ratio was set to Co-15Cr-8B-2Ta,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 70%,and the total rolling reduction of the secondary rolling was set to2.9%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 103.4 μm², and the number of cracks in the B-rich phase was4500 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 8.

Comparative Example 24

As shown in Table 1, the composition ratio was set toCo-15Cr-12.5Pt-6B-1Ta, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1100° C., the total rolling reduction of theprimary rolling was set to 69%, and the total rolling reduction of thesecondary rolling was set to 3.5%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 97.9 μm², and the number of cracks in the B-rich phase was3700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 7.8.

Comparative Example 25

As shown in Table 1, the composition ratio was set toCo-20Cr-11Pt-4B-1Nd, and a target was produced according to the sameproduction process as Comparative Example 1. Here, the annealingtemperature was set to 1100° C., the total rolling reduction of theprimary rolling was set to 11%, and the total rolling reduction of thesecondary rolling was set to 1.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 120.1 μm², and the number of cracks in the B-rich phase was3200 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 3.2.

Comparative Example 26

As shown in Table 1, the composition ratio was set to Co-10Cr-25Pt-5B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 67%,and the total rolling reduction of the secondary rolling was set to3.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 94.8 μm², and the number of cracks in the B-rich phase was3000 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.1.

Comparative Example 27

As shown in Table 1, the composition ratio was set to Co-10Cr-18Pt-15B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 63%,and the total rolling reduction of the secondary rolling was set to3.4%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 162.3 μm², and the number of cracks in the B-rich phase was5300 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 9.7.

Comparative Example 28

As shown in Table 1, the composition ratio was set to Co-40Cr-10Pt-1B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 74%,and the total rolling reduction of the secondary rolling was set to0.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 91.2 μm², and the number of cracks in the B-rich phase was2600 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 0.2.

Comparative Example 29

As shown in Table 1, the composition ratio was set to Co-10Cr-1Pt-5B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1080°C., the total rolling reduction of the primary rolling was set to 73%,and the total rolling reduction of the secondary rolling was set to4.5%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 100.3 μm², and the number of cracks in the B-rich phase was2700 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 11.8.

Comparative Example 30

As shown in Table 1, the composition ratio was set to Co-10Cr-30Pt-5B,and a target was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1100°C., the total rolling reduction of the primary rolling was set to 69%,and the total rolling reduction of the secondary rolling was set to2.8%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 106.7 μm², and the number of cracks in the B-rich phase was2900 cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 10.9.

Comparative Example 31

As shown in Table 1, the composition ratio was set to Co-13Cr-8t-4 and atarget was produced according to the same production process asComparative Example 1. Here, the annealing temperature was set to 1090°C., the total rolling reduction of the primary rolling was set to 75%,and the total rolling reduction of the secondary rolling was set to0.0%.

As a result of analyzing this target with the same method as ComparativeExample 1, as shown in Table 1, the average grain area of the B-richphase was 92.6 μm², and the number of cracks in the B-rich phase was 120cracks/mm². Moreover, the maximum magnetic permeability in thehorizontal direction relative to the sputtering surface was 51.2.

While all Comparative Examples (excluding Comparative Example 31) had amaximum magnetic permeability (μ_(max)) of 50 or less, they had a largeB-rich phase having an average grain area that exceeds 90 μm². In caseswhere the B-rich phase was large as described above, the B-rich phasewas subject to more than 2500 cracks/mm². This kind of structure causesthe generation of arcing, causes the discharge during sputtering to beunstable, and increases the generation of nodules or particles.

The present invention yields a superior effect of being able to providea sputtering target for a magnetic recording medium that has few cracksin the B-rich phase and has a high leakage flux density. It is therebypossible to stabilize the discharge during sputtering, suppress arcingwhich occurs from cracks in the B-rich phase, and effectively prevent orsuppress the generation of nodules or particles. Moreover, the presentinvention yields a superior effect of being able to form a high-qualityfilm and considerably improve the production yield.

Since the sputtering target for a magnetic recording medium of thepresent invention possesses superior characteristics as described above,it is effective for forming a magnetic thin film for a magneticrecording medium, particularly a magnetic film of a hard disk.

We claim:
 1. A sputtering target for magnetic recording medium obtainedby rolling a Co—Pt—B-based ingot, wherein an average grain area ofB-rich phase is 90 μm² or less, and wherein the sputtering targetconsists of 1 to 26 at % of Pt, 1 to 15 at % of B, 0 at % or 1 to 10 at% of one or more elements selected from Cu, Ru, and Nd, and remainderbeing Co.
 2. The sputtering target for a magnetic recording mediumaccording to claim 1, wherein a number of cracks in the B-rich phase is2500 cracks/mm² or less.
 3. The sputtering target for a magneticrecording medium according to claim 1, wherein the sputtering target hasa maximum magnetic permeability (μmax) of 50 or less.
 4. A sputteringtarget for magnetic recording medium obtained by rolling aCo—Cr—Pt—B-based ingot, wherein an average grain area of B-rich phase is90 μm² or less, and wherein the sputtering target consists of 1 to 40 at% of Cr, 1 to 26 at % of Pt, 1 to 15 at % of B, 0 at % or 1 to 10 at %of one or more elements selected from Cu, Ru, and Nd, and remainderbeing Co.
 5. The sputtering target for a magnetic recording mediumaccording to claim 4, wherein a number of cracks in the B-rich phase is2500 cracks/mm² or less.
 6. The sputtering target for a magneticrecording medium according to claim 4, wherein the sputtering target hasa maximum magnetic permeability (μmax) of 50 or less.